The invention relates to filter connectors and in particular to a filter connector with frame for a filter unit having a flat substrate with a pattern of passages for the contact elements of the connector.
In order to surpress interference signals of higher frequency, it is advantageous in practice to use a filter unit which can be connected to the contact elements of a connector, such as is described in, for example, applicant's copending U.S. application Ser. No. 07/211,253 filed June 24, 1988 and in U.S. Pat. No. 4,791,391. granted Dec. 13, 1988 and U.S. Pat. No. 4,682,129 granted July 21, 1987, all assigned to the same assisgnee as the present application. Such a filter unit in general comprises a flat, electrically non-conducting substrate on which capacitor elements are formed. These capacitor elements are provided with passages for the connection ends of the contact elements and comprise at least one common electrode which can be connected near the ends of the substrate, and at least one electrode patch which is separated therefrom by means of a dielectric and surrounds a corresponding passage. The electrode patch is connected to the connection end of a contact element such as a terminal pin and the common electrode is connected to a shielding of electrically conducting material which encloses the contact elements of the connector. In general, this shielding is connected to the ground of an electronic circuit.
It has been found, particularly in the case of geometrically extended filter units, that the difference in coefficient of thermal expansion of the filter substrate compared to the shielding of a connector can lead to such undesirable mechanical stresses. For example, ambient temperature increases can cause the substrate or, for example, the common electrode to break.